The present invention relates to an improved pet door.
A typical, basic pet door comprises a frame defining an opening or portal and a pivoted closure flap, usually top-hung in the opening. Such a pet door when mounted in a door, window or external wall allows a pet to enter or exit a building at will, by pushing aside the flap. Regrettably unwanted animals can also enter the building through such a pet door.
Some commercial pet doors have a flap locking device which enables the pet owner to control the freedom of a pet to pass through the pet door. See, for example, our GB patent No. 2 142 070. Such a device may be set to allow passage in and out, to allow passage in one chosen direction, e.g. in only, and to bar passage in and out. "In" and "out" mean into and out of the building. Unwanted animals are not prevented from entering a building when the flap locking device is set to allow passage into, or both into and out of, the building.
To guard against unwanted animals, e.g. stray cats, entering a building, so-called selective pet doors have been developed. Selective pet doors have a latch which secures the flap against opening in at least the in direction, and means to retract the latch freeing the flap when the owner's pet approaches the pet door.
One such pet door, our Staywell (RTM) No. 21 pet door, embodies a sophisticated electronic circuit to control a solenoid for retracting the latch itself. The circuit is activated when the pet, wearing a collar bearing a passive inductive key element to which the circuit is tuned, closely approaches the pet door. The circuit can be tuned to respond to a large number of different inductances, or key "differs". Thus, even though there may be a substantial number of these pet doors in a neighbourhood, and hence a substantial number of pets wearing keyed collars, only each owner's pet can enter its building. This system is disclosed in our GB patent No. 2 119 431.
Another pet door, which will only allow passage of a pet wearing a key collar, is magnetically-activated. The key element is a magnet. When it is brought into close vicinity of the pet door, the key activates a magnetic reed switch to close an electric circuit which energises a solenoid, the latter then serving to retract the latch and free the flap. This, selective pet door can only distinguish between a pet bearing a key magnet from an animal bearing no such key magnet. This system is disclosed in GB patent No. 1 588 673.
Selective pet doors such as outlined are relatively costly. Another drawback is that they need a source of electrical energy. If mains electricity is used, there are the costs and complications of transforming the supply and of installation. If battery power is used, batteries will require replacing at more or less frequent intervals. Thus, the above selective pet doors may not be ideal for everybody.